I cannot speak for Barrett, but my understanding is that the chassis failures were addressed with the revision and have been replaced.
You must understand that a large scale rifle program is going to expose ANY weakness in a design and will require revisions and evolution to take care of unforeseen circumstances. I won't pick on anyone specific but a lot of times you see new rifle designs introduced that may look great, but if you were to field hundreds of them and put them through the rigors of the US Army training regiment and use case there will be issues that bubble to the surface that would be nearly impossible to identify during T&E. Throwing rifles around, running them in all sorts of conditions, running up round counts, passing through the hands of many shooters are all elements that will contribute to finding these sorts of issues. Just look at the thousands of MRADS in civilians hands and I have not seen anyone identify or replicate the issue.
With that said, it is absolutely the responsibility of the manufacturer to acknowledge the issue and remedy it. I suspect Barrett will be searching for a solution to ensure the Mk22 doesn't end up like the Mk21.